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Do your nuts rise when jiggled?

I love a good Benny Hill moment. This is a make yourself a little smarter post so pay attention blogophytes’ Here is a test for you – get a box of muesli that contains nuts and jiggle it.

Surprisingly after vigorous jiggling the heavier nuts have risen to the top and the lighter other bits and pieces have sunk to the bottom. This paradox is known as the Brazil nut problem and it has intrigued physcisits for years and annoyed engineers for whom unmixing within during factory processes is a right pain in the bum.

Interestingly, this is a source of argument as to the mechanism of this phenomena. At first it was postulated that the process of a nut moving higher up a mixture column created room below it for the lighter flakes and like to infiltrate the gaps.

For a gap to open up for a nut to fall several flakes would have to move out of the way which was considered unlikely. In this process the nuts in effect ratchet their way up. A reasonable hypothesis but apparently one that has not satisfied physicists entirely.

Sidney Nagel of the University of Chicago has suggested that the cult of the rising nut is a function of the shape of the box which when shaken allows nuts to rise to the top of the box whilst further shaking causes the oats and smaller flakes to slide down the side of the box leading the nuts marroned at the top of the box.

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